When a conventional silver halide photographic material is exposed to light and subsequently color developed, and aromatic primary amine developer oxidized thereby reacts with a dye forming coupler to form a color image. In general, this method utilizes color reproduction by a subtractive color process, and in order to reproduce blue, greem, and red, color images of yellow, magenta, and cyan, which are in the complementary relationship thereto, respectively, are formed. For forming cyan color images, phenol derivatives or naphthol derivatives are often used as couplers. In color photography, the color forming coupler is either added to a developing solution or included in a photosensitive photographic emulsion layer or other color image forming layer, and by reacting with an oxidized form of a color developer formed by development, a nondiffusing dye is formed.
The reaction of the coupler and the color developer takes place at the active site of the coupler (referred to as the "coupling position"), and a coupler having only hydrogen atoms on this active site is a four-equivalent coupler, i.e., stoichiometrically requiring 4 moles of silver halide having developing nuclei for forming 1 mole of dye. On the other hand, a coupler having a removable group as an anion at the active site is a two-equivalent coupler, i.e., a coupler which stoichiometrically requires only 2 moles of silver halide developing nuclei for forming 1 mole of dye. Therefore, as compared with the 4-equivalent coupler, since the amount of the silver halide in the photosensitive layer may be lowered and hence the thickness thereof may be reduced, it is possible to shorten the time required for processing the photosensitive material, and furthermore, sharpness of the formed color image in enhanced.
Of the phenol type couplers and naphthol type couplers known as cyan color forming couplers, it is disclosed, e.g., in Japanese Patent Application (OPI) Nos. 65134/81, 204,543/82, 204,544/82, 204,545/82, 33249/83, 33250/83 etc. (the term "OPI" as used herein refers to a "published unexamined Japanese patent application"), that phenol type couplers having a phenylureido group at the 2-position and further an acylamino group at the 5-position are superior to the other cyan couplers in light fastness of the color images formed by color development.
However, most of the phenol type two-equivalent couplers having a phenylureido group at the 2-position, an acylamino group at the 5-position and a removable group at the 4-position have some drawbacks. For example, the coupling activity is insufficient, color fogging is easily brought about, dispersibility is poor and coating problems occur, the coupler itself is unstable and cannot stand long-term storage, and so forth.